sites this was the most populous and the administrative headquarters for the whole manhattan project and the majority of people working there were young women. >> jon: right and it was 75,000, 80,000 people. >> 75,000 people and when they first broke ground in 1942 and were planning to build they thought 13,000. we'll probably have 13,000 people living here. by the middle of 1945, 75,000 people, plants running 24-hours a day, 24-hour bowling and roller skating. it was a massive, massive town. >> jon: the crazy thing is they have no idea what they are doing there. >> yes, yes. there's that part, yes. so the majority of people who worked there were trained to do very specific tasks. for example, you are testing pipes. >> jon: sure. >> pipe comes in. how are these welds?